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Why don't airliners use in-air refueling systems?
Right now if an airliner wants to fly a really long distance (eg., a Boeing 787 flying from Seattle to Tokyo), it has to load itself down with lots and lots of fuel, which in turn weighs thousands and thousands of pounds.  This, of course, makes the flight of the aircraft less efficient than it could be1.  Thus, if the craft could theoretically carry half as much fuel, that should increase the fuel efficiency of the craft, right?2
Mid-way refueling seems like it would be a Good Idea™ at that point.  Of course, landing would add a heck of a lot of time to the flight, so it seems the better option would be mid-air refueling.  It would allow for the aircraft to be more efficient, without the need for stopping on a long journey.
Boeing and Airbus both make a few airplanes | that can do | mid-air refueling, in fact one of them is a highly modified 747-200 (properly called a VC-25) used as Air Force One:

(source: wordpress.com)
I assume that, because Airbus and Boeing's engineers and sales managers are really quite smart, they have a really good reason that they don't fit/sell this feature on any civilian transportation aircraft.  But I'm not sure what that reason is.
Does anyone know why airlines do not use aircraft that are capable of mid-air refueling?

1 If I'm not mistaken, increased weight means an increased AoA to maintain level flight, which in turn increases induced drag from the wing.  Less fuel would mean less induced drag or, if mid-air refueling were common practice, a wing that was designed to be more efficient because it was required to handle less weight.
2 I don't know by how much, if it's not that much, well, that might explain why nobody does this.

Safety and logistics aside, I'm not sure the benefit of having another large aircraft burning fuel to refuel another aircraft burning fuel would offset the cost of just taking off with a larger fuel load to begin with.

@RhinoDriver And that'd be especially true if the refueling plane had to fly a long way out of it's way to get to a single airliner.  Where as the way the military uses them...is quite different I assume.  Actually if you have a moment to describe the difference in mission (ie., answering this from the "why the military uses mid air refueling" perspective) in an answer, that would be really cool.  Especially since you know directly :).

No problem Jay. Aerial refueling is a very expensive endeavor with very few practical uses. For the military, the increased price of fuel is well worth the increased tactical ability our aircraft receive. Whether that's playtime in a kill box, or blue water operations in the Navy (ie, no divert, where the carrier is the only option and being low on fuel requires a tanker), there are a myriad of tactical and administrative benefits the military pays for through aerial refueling.  I'll post an actual answer later when I've got a bit more time.

Regarding your footnote number 1, for airliners, I think airliners tend to just fly at a lower altitude with more dense air rather when they're heavy rather than using a significantly higher AoA, but, either way, you're right that it means more drag and, therefore, more fuel burn.

It seems to me like simply making more stops to refuel a smaller tank would use less overall fuel, as the refueling plane has to take off with the extra fuel and land without it (just as actually landing and taking off would) but has the added overhead of a second plane.

I'm not sure safety can be set aside... ATC exists expressly to keep airliners apart, putting two very large aircraft in close proximity, (10's of feet separation), one carrying an enormous fuel load and one carrying human cargo, is a recipe for disastrous inattention.

A question for all: how many flights are flown today that require a stop for fuel within the flightplan?

Caveat: the pictured 747 is not Air Force One, it is an airborne command & control platform called the E-4B

@JayCarr not sure too many passengers would enjoy all those extra hours confined to their economy seats

@SSumner Ah, you caught me.  I couldn't find a good picture of Air Force One being refueled (in a reasonable amount of searching), so I went with something that looks very similar.  I actually almost went with a picture of an Iranian command plane, but decided it would be too obvious :).  https://upload.wikimedia.org/wikipedia/commons/f/fa/IIAF_Boeing_707_refuels_IIAF_Boeing_747.jpg

Boeing has also made a few dozen 737s that are capable of in-air refueling: the P-8 and the 737 AEW&C / E-7A.

Given that the longest haul non-stop commercial flight is some 13,800km https://en.wikipedia.org/wiki/Non-stop_flight  it would seem that airliners can pretty much fly as far as any commercial need would require. To put it another way, there is probably not enough economic benefit, and the solution to "not enough range" for commercial aircraft seems best addressed by increasing fuel capacity or making intermediate stops. Bear in mind that military and civilian aviation operate under different economic, safety, and logistical priorities, so what's good for one may not be for the other.

The line of answers to this question is interesting, but regarding 'costs', figures, real world figures, are the comments' best friends. Blessings +

Fuel Quantity Unlike smaller fighter jets, you would need to offload a substantial quantity of fuel. For a B777, you're looking in the range of 60 tonnes of fuel for half a tank. The boom of a KC-135 (faster than a basket) can do around 3 tonnes a minute. The math comes to then 20 minutes of aerial refuelling. The KC-46 can do perhaps 180 tonnes, so you might squeeze out three refuelling operations from one flight.
Risk This is considerably more dangerous than the very conservative safety margins aircraft normally operate within. You would have one aircraft filled to the brim with fuel, and another aircraft with 300+ passengers. A quick search on YouTube is enough to propose this entire thing is very dangerous.
Furthermore, you need to consider that the aircraft needs safety margin to divert should refuelling not work, which cuts into the benefits you can expect.
Many intercontinental routes will be flown at night, making the manoeuvre more difficult.
Refuelling Area Looking at the route you proposed, the closest airfield would probably be in Alaska, at least 500km away. Guess another relevant area would be Iceland/Greenland. Even if you did reroute, you'd get away from the jetstreams that aircraft over the Pacific use lying considerably further south, reducing efficiency. The same scenario applies for eastbound Atlantic flights.
Expensive You would need to get another aircraft (~$200m for a KC-46) with special equipment and crew training. The receiving aircraft crew would also  need special training. The airframe modifications would be complicated and require certification. Furthermore, you would need to get everybody to agree on some common standard.
Logistics Planning is difficult. Each aircraft would have to be rerouted to intercept the tanker at a certain time and place. You want to refuel them perfectly one after an other, which is almost certainly not possible. There's just not the volume of aircraft movements feasible for this, especially for the ultra-long flights where it may have the greatest benefit.
Other Landing Benefits
Include changing crews and possibly offloading passengers.
Applicability
The number of flights where this can be practically implemented and used is very limited and for all intents and purposes, you can just land the plane itself and refuel it. Even for the route you propose, it's around 7,500 km which is not a lot for a B777.

Regarding risk - I could only find two accidents involving mid air refueling, both were from the 60s.  Expense - Maybe, but do you have a moment to talk about possible fuel savings across hundreds of flight v. the cost of that one plane?  Logistics - Don't you think an airline could handle that though?  They put up with odd logistics all the freaking time.  Other Landing Benefits  - I was particularly talking about flights that are already non-stop.

Also not sure 20 min is that big of a deal (but suddenly starting to wonder if this questions is going to work well in this format, perhaps I should be in chat for this...)

Keep expanding the answer though, they are at least good thinking points

Other routes might also find this useful & for those lot of tanker bases would be practical options. e.g. the direct flights from East Coast USA / Mikdwest USA to South Asia carry a lot of fuel too.

Even the Air Force, with lots of experience in this, says in their tanker manuals: "Because of the magnitude of interrelated aerodynamic effects flying two aircraft at close vertical proximity is unsafe."

@JayCarr Over the 10 years between 1978 and 1988, the USAF had 279 refueling mishaps causing at least $10,000 in damages or at least one injury.

Yes I agree with Jay Carr, thee amount of crashes I have seen (not personally seen) and heard about in the 60s, was so frequent that it was generally banned. Plus you'll need to pay the expense for the extra fuel which someone told me about.

@cpast lol, noted.  I wonder if both your comments (and citations) could be put in the answer to help support it?  I assume there are lots of good reasons that I'm unfamiliar with so...  yeah, a comprehensive answer would be great.

@Jo7 lol, that's not what I was saying, I was saying I hadn't seen many accidents in my google searching, and I was hoping someone would come along and show me some stats.  Which cpast did, so I think we're good :).

Actually Iceland is a "pleasant place" for aircraft operations, being at low altitude, nice and cold all year round, and with no short-haul domestic routes! I can remember when all the records for "least unscheduled maintenance," "lowest IFSD rates," etc on the B757 were held by Icelandair. The only problem is the occasional volcanic ash cloud. Greenland, being mostly 9,000 ft mountains, is a different story, of course.

@alephzero I stood under the impression that the place was hammered by high winds and snow for a fair bit of the year...

In terms of relative risk levels, regardless of the frequency of mishaps the military have with in-flight refueling, note that civilian aviation is MUCH more risk-averse, and the length of a refueling boom is somewhat less than the usual separation that the FAA tend to operate under, which are 1000ft vertically and 3 miles horizontally.

@MikeFoxtrot I think you can add one other benefit of landing over in-flight refueling: nice for the passengers to be able to exit the aircraft after a while. Eight hours is a long time (I would say too long) to be cooped up in an economy cabin, and there are airliners already in revenue service capable of significantly longer flights. IMHO a more passenger-friendly way to go further in a single hop would be to go faster rather than stay up longer.

Don't look at the fuel consumption of the airline flight in isolation. An airline would need to combine the fuel used by both the revenue-earning flight and the tanker, and then add the cost of operating it, too. Even if this could be shared by four or five revenue-earning flights, the total would still be worse.
To find out how big the fuel saving by in-air refueling is, the Breguet equation is your friend. Let's assume an L/D of 18, a thrust-specific fuel consumption of $b_f$ = 0.018 kg/kNs and a speed of Mach 0.82, which equates to $v$ = 279 m/s in 11.000 m altitude. Now look at the mass fractions which go with ranges of 8000 km and 2$\cdot$4000 km:
$$\frac{m_1}{m_2} = e^{\frac{R\cdot g\cdot b_f}{v\cdot L/D}}$$
Flying the distance in one go needs the plane to start with a fuel load equivalent to 32.5% of the landing mass, while an air-refueled flight needs only 2$\cdot$15.1%. The saving (fuel equivalent to 2.3% of airliner's landing mass) is real, but even if four others could benefit from the same tanker flight, it would need to cost less than the equivalent of the fuel price of 5$\cdot$2.3% = 11.5% of the airliner's landing mass.
Since the tanker needs to carry 5$\cdot$15.1% = 75.5% of the airliner's landing mass in fuel, it needs to be an airliner-sized aircraft itself. Add more if the tanker needs to do even as much as to take off, let alone fly to a refueling point and wait there. And the fuel saving needs not only to pay for the tanker's fuel needs, but also for its crew, maintenance and depreciation.
Aerial refueling is a great technology to make complex military scenarios possible, but is a very ressources-hungry beast.

It seems like the tanker just taking off and climbing up to the cruise altitude of an airliner would burn quite a lot of fuel... and that's if it would even be possible for a tanker loaded down with Jet-A to even climb up to the altitude of an airliner with light fuel load in the first place. If the airliner has to descend to meet the tanker, that's yet more wasted fuel.

Might it become slightly more feasible if they used smaller planes for the flights?  Like a B738, or A319?  Maybe even a CR-145?  Then you could have one tanker carrying fuel for several planes.  Granted this doesn't address a whole list of other problems but...theoretically would it help?

@JayCarr: Using smaller passenger planes will make longer-range connections possible. Now we save not just some fuel, but make flights possible which could not be flown before. However, smaller planes are less efficient, and more cramped on the inside. The seat-mile fuel consumption would be larger, and I certainly will not look forward to flying transcontinental flights in a CR-145!

Looks like we can save, in perfect world, around 9.3% of total fuel.  Assuming fuel is $5 a gallon, and a 50,000 gallon capacity (777 long range seems to be just under that) there's a potential for a $23k saving in fuel.  Bigger than I would have expected, but I doubt big enough to justify the cost of a second aircraft.

@NPSF3000 MikeFoxtrot quoted $200m for a KC-46, so let's go with that and your $23k savings per flight. In fact, let's make it $25k/flight, and four refuelings per KC-46 flight, so each KC-46 takeoff saves $100k. That's 2,000 tanker flights until break-even. But that's before you have any people to fly or care for the tanker. Even assuming a perfect world, that's many thousands of trips for the tanker before break-even. The world is not perfect. One mishap and that carrier might very well be facing bankruptcy. People understand that crashes happen, but deliberately putting that fuel there?

@MichaelKjörling until you put it like that, I never really realized how expensive a $200Mn aircraft really is!

2019 update: site is dead (now a scam service). See wayback machine here:
The people from Cruiser-Feeder http://www.cruiser-feeder.eu/ try to make it happen.
Here is part of the abstract from a paper describing their approach:

In this paper it will be described how the safety of air-to-air refuelling has been assessed, and how
  proposed new or amended regulations and acceptable means of compliance have been defined

They even created a conceptual design of joint-wing tanker for civil operations: http://www.cruiser-feeder.eu/downloads/li-la-rocca---conceptual-design-of-a-joint-win.pdf
In their papers, you will find data for which flights mid air refuelling is worth it, how they want to make it happen, and some interesting facts.

Interesting approach: Let the tanker fly behind and push the fuel up. This requires much less training of airliner crews. But when I see a joined wing proposal, I know this is from an academic ivory tower with little practical experience in aircraft design and construction.

@PeterKämpf, you mean sometimes theories don't work so well in the real world? I'm shocked!

@FreeMan: I am even more shocked. The dishonesty (or is it cluelessness?) of the people behind the cruiser-feeder website is breathtaking. They are happy to gobble up EU research funds with unbelievable claims. A simple back-of-the-envelope calculation shows that the benefits are merely a tenth of what they claim - just for the isolated airliner. System fuel consumption will go up.

@PeterKämpf unfortunately I don't have much experience in this field of the wide aviation world, I posted the answer because I think it's definitely worth a read. Why are you so shocked about the cruiser-feeder concept? I think the idea behind the concept is very good. Let the plane start with a little amount of fuel to reduce its start weight and then refuell it in the air on its way to the destination. Why do you find a joined wing proposal a bad idea? As I said, I'm not experienced in this field of aviatics but I'm interested in your opinion about the Cruiser Feeder Concept.

@jklingler: This concept will never be certified - just think what might happen if the refueling fails. In the end, the airliner will need to be much like airliners today, and with the Breguet equation it is easy to see that the savings are modest. I encourage you to ask new questions, because the comments make it hard to explain all details.

@FreeMan: The difference between theory and practice is that, in theory, there is no difference.


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What does DRMS OTS mean in a notam
MULTIPLE DRMS OTS ON RWY 34R/16L. 9/3 EAST/WEST SIDE. 8/4 EAST
SIDE. 6/6 EAST/WEST SIDE. 1/11 EAST SIDE. 18 APR 22:01 2024 UNTIL 31 MAY
23:59 2024. CREATED: 18 APR 22:01 2024
I have looked everywhere and all I could find for DRMS was Distance Root Mean Square which doesn't make any sense. This is a notam for OTBH.

I would say it reads multiple Distance Remain Marker(S) are out of service.

Welcome to Aviation.SE! That answer makes complete sense, especially given the rest of the info in the NOTAM. Good deduction!

source: Stack Exchange

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sort: votes


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Does the airspeed indicator measure speed inaccurately at different angles of attack?
A point of confusion for me has been this: Does the pitot tube measure the airspeed of the plane in the direction of its flight path, or does it measure the speed of the air parallel to the pitot tube itself. For instance, in a Cessna 152 that may be in a decent but the nose is not pointing down as sharply as the decent path, is the pitot tube accurately measuring the downward speed along the flight path, or is it only measuring accurately the speed of the air parallel to the direction the pitot tube is pointing?

Related

Also, the pitot tube doesn't measure speed at all.  It measures pressure.

@CamilleGoudeseune: and the air speed indicator (ASI) doesn't indicate air speed, but pressure difference.

Error increases with AoA.  A  sustained indicated reading of 35 knots was observed in a 172 at full power in slow flight (at altitude).  If anything, the lower IAS readings provide a safety margin to help avoid stalling, but the error is less as AoA decreases.

@CamilleGoudeseune that error is for a “venturi-shrouded pitot probe”, which is something like magenta unicorn. For normal pitot the error becomes significant much earlier.

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Mandatory Reports to ATC on an Approach
An instructor recently told me a required radio call to ATC is to tell them when you are established on course on final approach. His point was that this tells ATC when to switch you to tower. While I see is point this seems more like technique than procedure. I have not been able to find this written anywhere. The AIM does provide a list of times when the pilot should make reports to ATC: 5-3-3.a.1. But this list does not mention reporting when established on a segment of an approach or when established on final. Is it written anywhere else what other required calls might be to ATC e.g. over the FAF, established on course on final?

Whenever you hear claims of a requirement you should respond, "interesting, I didn't know that, would you please show me where it says that so I can reference it in the future?"

It's absolutely not required, and would be a lot of needless clutter on the frequency.
Listen to LiveATC or something similar for the final controller at any busy airport like LAX or Atlanta or really anywhere with a continuous stream of aircraft being cleared for ILS approaches, and you'll find that pilots don't report any such thing.
The typical transmissions are,

Approach Controller: Bigjet 123, fly heading 030, 3000 feet until established, cleared the ILS 36L approach.
Aircraft: Bigjet 123, heading 030, 3000 until established, cleared ILS 36L
Controller: Bigjet 123, contact tower 127.85
Aircraft: Bigjet 123, tower 127.85

That's about it.
Now, if the controller tells you to report established on final, then obviously you'll do that.  And if you're using non-radar procedures, those have a lot more calls.  But for the typical case, reporting established on final isn't a thing, and would be extra radio traffic to no point, and/or creating confusion of "why are they reporting that???"


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Does the FAA provide a CFI knowledge test guide?
The FAA provides the Airman Certification Standards (ACS) for commercial pilots. It discusses the topics asked on the knowledge test. I have only been able to find the Practical Test Standards (PTS) for the Certified Flight Instructor (CFI) practical test. Does the FAA publish a similar document discussing what topics are covered on the knowledge test?


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Holding Airspeed at Military Fields
I read in the AIM, 5-3-8 j.2.b.3 that holding airspeeds at USAF airfields only are 310 KIAS maximum, unless otherwise depicted. I interpreted this to mean that any holding pattern on an approach plate for a USAF airfield unless published otherwise had a max speed of 310. An examiner claimed that actually it means that the max speed of 310 applies only to holding patterns based off of the navaid located directly on the airfield. I have not seen that written and I think the correct interpretation is the one that assumes that the max airspeed applies to any holding pattern associated with an IAP at a USAF field unless published otherwise.

I'm with @RTO.  That speed has more to do with performance range of USAF aircraft types than the holding point references.  Stubby winged airplanes don't like being "too slow."  I think about the T-38 for example which is well known for potentially getting in trouble quickly in a base turn, or when circling where the '38 is a category E.

Can you provide an example chart? I think the examiner may be closer to correct in actual practice. For many military procedures, civilian NAVAIDs are used for arrival holding patterns. The 8260-2 form for that NAVAID will indicate all of the procedures that it is used on, and the restrictions. It would not surprise me that an otherwise ‘standard’ holding pattern would not show a speed restriction.


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Why are flights not also restricted during abnormally low barometric pressure conditions
FAR 91.144 talks about restricting flight operations during abnormally high barometric pressure conditions. Why would there not be an identical restriction during abnormally low barometric pressure conditions?
This seems to be the more dangerous situation. In the "abnormally high" situation, if the altimeter can only be set to 31.00 and below, then it will tell you you are lower than you are, which gives a safe bit of padding. In the "abnormally low" situation, if the altimeter setting drops below 28.00 and the altimeter can't be set any lower, then the pilot has no padding and is actually lower to sea level than the altimeter says he is.

Typical low pressure goes down to around 29.20 while typical high pressure is around 30.60. This means that the pressure is more likely to exceed 31.00 than to be lower than 28.00.
The weather is also a factor. Higher pressure is generally associated with good weather for flying, while extreme low pressure is associated with major storm systems where you wouldn't want to be flying anyway. Even many major storms don't drop below 28.00 at their lowest point. Just looking at the cyclones so far this year, anything below 28.00 (948 hPa) has winds peaking over 100 mph.

Covariance pressure/wind, from this study.


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Would blade-less (Dyson style) jet engines work?
Is it possible to design an aircraft with blade-less (same concept as Dyson) design to generate thrust?
What are some of the key benefits, drawbacks and examples of attempts (if any) at this kind of design?
Envision the engine/s:

Are mounted inside the fuselage. E.G. in the cargo area (ofc this means reduced space for cargo)
Have an intake which allows for air to enter the engine for compression
Thrust-points are located throughout different point/s of the fuselage/wing

Here are some (faux) examples of what this concept could sort of look like:

It seems like this type of design could reduce drag and therefore improve efficiency. Plus the added benefit of reduced noise and impact of bird strikes.
Here’s an article which explains how Dyson fans work for reference: https://electronics.howstuffworks.com/gadgets/home/dyson-bladeless-fan.htm

Thing is, the "bladeless" bit is a bunch of marketing BS.  There are oodles of blades; they are just hidden inside a housing and are used to create a high velocity stream to pull along a low velocity stream.  In other words, an ejector pump.  A useful mechanism if you want to move air using a handy motive source that would otherwise be wasted. An extremely inefficient way to accelerate a mass of air for thrust purposes.

The photos showing a superficial resemblance between an empty nacelle and an allegedly bladeless fan, (that actually isn’t) severely hamper the credibility of this question in my opinion. (I.e. it looks like it’s asking “can we just remove the engine and still produce thrust?”)

Oh, kinda funny the preceding dyson fan question has 53 fans (atm). Pun inteded.

No that has no benefits for aviation at all, except for the marketing department. A large amount of losses funnelling the airflow from motor to a small strip, from which it is propelled at high velocity.
As stated in many places on this site, thrust T = $\dot m \cdot \Delta V$, while the energy expelled E$_{kin}$ = $½ \cdot \dot m  \Delta V^2$. So thrust efficiency is highest when the largest amount of air flow is accelerated least. And this is exactly opposite of what the Dyson fan does.
So a propeller with large blades, accelerating air directly backwards, is the best.

+1, but this arrangement would be less vulnerable for FOD, so there is some merit here. The engine providing the compressed air would of course still be more or less susceptible to FOD. As for efficiency, this arrangement would be catastrophic.

Would it really be less vulnerable to FOD? Where would the air inlet be, on top of the aeroplane?

I'm going by the guess that the actual engine would have a single intake, compared to multiple intakes of engines on wings or fuselage, so just by area it might be a tad bit "safer". Then again, because of the losses, the main engine would be huge, so...


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When is a circling only approach made
I've read online that if the final approach course alignment is more than 30 degrees, or if more than a 400 feet per nautical mile descent rate is required, that a circling only approach must be made. But no one ever cites the source for either of the two conditions. Where is the source for those two conditions? Page and paragraph number?


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If an Airport has only a VCOA and a SID, does the VCOA count as an ODP, and if not, does that mean you can fly a diverse departure?
KGRF has a SID requiring a climb gradient of 469 FPNM for obstacles. In the takeoff minimums section, there are takeoff minimums listed for a VOCA (Visual Climb Over Airport)  but nothing else. My understanding was that a VCOA was an alternative if you did not want to fly an ODP (Obstacle Departure Procedure). But this airport only has a SID (and no ODP?)Which would lead me to believe that you could fly a diverse departure out of this airport. However if you could fly a diverse departure, what would be the point of even having a VCOA since the required climb gradient for both would still be 200 FPNM?

@757toga, isn’t that the purpose of a VCOA? It enables one to depart without having to meet the climb requirements of an ODP. It’s technically not a procedure (nor is DVA), but it is a way of departing IFR.

@Anthony Schrayer, this is probably an error on the Army’s part. If I had to guess, there should be a “Diverse departure not authorized” under the section DEPARTURE PROCEDURE (not shown). The clues are that there is no mention of takeoff mins other than for VCOA and the SID departure for Rwy 33 is supposed to be for military only (apparently). There is a lot wrong with this situation.

@757toga, I think you’re slightly mistaken regarding the climb. An ODP can definitely have greater than a 200 ft/NM requirement. Typically the takeoff mins would say something like “Std with min climb of XXX ft/NM to .” What you would not expect to see is a VCOA without also having a non-standard takeoff and/or climb requirement minimums.

@757toga, yep I interpreted your “may not” as not permissive rather than optional. We’re on the same page, thanks.

"RADAR REQUIRED" and Diverse "Vector", VCOA is non-radar. There are times when an aircraft cannot achieve initial climb gradient or, more likely, will not be able to climb to some required minimum crossing altitude near the start of the route due to the short distance to join the airway. This is especially likely in mountainous areas. 200ft/NM slope is not strictly required of all IFR aircraft, it is only the assumed climb for airway design, aircraft that cannot meet this(maybe a tailwind or near service ceiling or both) must calculate an earlier start of climb. VCOA provides this head start.

Edited based on new information…
I communicated with both the procedure designer for Gray AAF and with the FAA’s Flight Standards office. There are 2 answers for this question:
First, the VCOA at Gray was created for ATC purposes rather than obstacle clearance, so this is not a good example for the question asked. The procedure designer says that you can fly a diverse departure at this location.
Second, per the 8260.46J (and has been the case for several of the previous iterations), “When the Flight Procedures and Airspace Group will not approve a CG in excess of 500 ft/NM (600 ft/NM for helicopters) and any of the obstacles forcing such a CG are located outside the ICA (extended) greater than three SM from DER; a stand-alone VCOA procedure may be used as the only option available for obstacle avoidance.”
Therefore, in general the VCOA may be the only option. This, however, is the only time a stand-alone VCOA would occur. Otherwise, one should expect to see a climb gradient higher than standard, takeoff mins higher than standard, or an ODP in addition to the VCOA.

VCOA is as it says "visual" and does not provide any obstacle clearance surfaces, therefore it is not an instrument procedure despite its primary usefulness being the start of an IFR flight. It is better classified as a maneuver. It also doesn't require radar services.

@Timbo How is it that that obstacle doesn't require an ODP on every runway? If you takeoff any runway and then turn immediately out of the ICA towards that peak with a standard climb gradient you won't make it anywhere near the altitude required to clear it.

I believe you can not fly a diverse departure if a VCOA is published. (Unless you're part 91, in which case takeoff minimums and ODPs aren't mandatory to begin with). The takeoff minimums say "9900-5 for VCOA," not "9900-5 for VCOA or standard otherwise."
There is some support for this in TERPS standards. From Volume 4, 1.4.6:

b. Where obstacles more than 3 statute miles from the DER penetrate the
OCS:

b. (1) Publish standard takeoff minimums with a required CG to a specified
altitude, and
b. (2) Develop a VCOA procedure to an altitude that will provide obstacle
clearance without a CG, and/or
b. (3) Develop a specific textual or graphic departure route to avoid the
obstacle(s).

From the wording it's clear that (3) is not mandatory if (1) and (2) are published. That is, a VCOA (2) may be mandatorily published without an ODP (3).
An example of an airport where some runways have only VCOA published where a diverse departure is clearly not possible is KBIH. At KBIH, there is an obstacle only 17 nautical miles from the airport that is over 10000 feet above airport elevation. No matter what runway you take off from, if you turn toward that obstacle out of the initial climb area, you won't get anywhere close to clearing it with a 200 fpnm climb gradient. Such an obstacle is high enough that it can't exist anywhere within 46 nautical miles of the airport and still allow for a diverse departure.
KBIH does have ODPs published for other runways. But since each runway is analyzed separately under TERPS criteria, I don't see how this is really any different from an airport with only a VCOA published.

The trick is that a VCOA is in addition to #1. For KBIH, there is not a greater than standard climb mentioned for 3 of the runways. VCOAs are not standalone.

@Timbo #1 appears to be mandatory either way? #1 and (#2 and/or #3). Well, the English isn't super clear. The fact that they didn't publish #1 is odd, but it doesn't seem to me that it authorizes a diverse departure. In any case, objects definitely penetrate the OCS here.

I have sent an inquiry into the FAA. I’ll post what I find out. The problem, in my mind, is that a pilot could reasonably believe that a diverse departure was allowable since it is not explicitly stated otherwise. Per the AIM 5-2-9D, a pilot would expect a diverse departure unless one of those items (D1-4) appeared. A VCOA is not one of those and is only mentioned later as an “option” to fly.

General comment — DoD does not develop procedures in strict accordance with FAA Orders. In other words, you cannot infer specific applicability of these orders into a DoD procedure. For Gray AAF, the VCOA has nothing to do with obstacle clearance as it would per the .46.

@Timbo That's why I used KBIH as an example.

Sounds good, I'll wait for your followup.


text:
How is TSO C145 equipment different from TSO C146 equipment?
From the AIM1-1-18 c1)
C145 - "Airborne Navigation Sensors Using the GPS Augmented by the Wide Area Augmentation System"
C146 - "Stand-Alone Airborne Navigation Equipment Using the Global Positioning System Augmented by the Wide Area Augmentation System"
It appears like C145 refers to only a sensor and C146 refers to a stand alone system. What does this actually mean? How are they different in the airplane? The two different titles seem like they are saying the same thing in a different way.

Let's start by clarifying terms. GPS is a positioning system. It provides position, velocity, and time (PVT) data. Navigation involves getting from point A to point B along a defined path. PVT is just one part of that process.
Most large Aircraft have an FMS, which is comprised of many components. Most support multiple PVT sensor inputs; GPS, IRS, radio-navigation (DME/DME, VOR/DME, VOR/VOR). For example, Collins Aerospace produces a Multi-Mode Receiver (MMR), essentially an ILS receiver and a GPS sensor in one box. It also has a precision approach navigator (PAN) function that provide a GPS/LAAS (ILS Look-alike) capability. The GPS sensor is a stand-alone sensor that complies with TSO-C145. It provides PVT data to the FMS and to the ADS-B systems.
General aviation aircraft typically have a stand-alone navigator or integrated flight deck. The latter just packages most of the avionics behind a single user interface in one or more displays. The key difference here is that the navigation functions (the nav database, path definition, path steering, and controls) are all packaged as a bundle. These are then certificated as a GPS Navigator under TSO-146. A common example would be the Garmin GTN series.


text:
Why does the airplane manual state S1 is equal to or greater than the higher of ground minimum control speed or critical engine failure speed
I don't understand why S1 is equal to or greater than the higher of Ground Minimum Control Speed or Critical Engine Failure Speed (Vcef). I do understand that S1 has to be the lowest of Refusal Speed, Rotation Speed, and Max Braking Speed.
Take a situation where Vcef is 100 knots, and the upper bound for S1 is 120 knots. It would seem that the only factors that should matter in determining S1 would be the three speeds that determine the upper bound. Why does the manual even talk about the lower bound if you are always taking the upper bound as S1.
What is so special about Vcef that we have to be above it? I would think that being below it is not a bad thing since it would take less room to stop than it would to lift off if you lost an engine.

@757toga Manual for the T-1A. S1 is the go/no go speed also known as V1

Having passed V1, you're committed to continuing the takeoff.  If an engine fails after V1 but below VMCG, you have no viable option: you can't stop (you've already committed to continuing the takeoff), but you can't control the aircraft laterally.
The only thing that could be accomplished in that case -- and you're a test pilot doing so -- is to reduce the power on the operating symmetric engine and hope that you can find some power setting that gives both enough directional control and enough thrust to continue to takeoff and accelerate.  The conventional wisdom is that this situation is unacceptable, and therefore V1 should not be lower than VMCG so that a crew isn't in that situation with no definite solution.
There is an unusual case where that risk is accepted; in C-130 "Max Effort Takeoff" procedures, it was allowed (when approved by the chain of command) to take off without that restriction; the idea being that in wartime operations, you accept the risk of an engine failure in the few seconds between V1 (calculated without considering VMCG) and VMCG in order to conduct the military mission on the short runway.  The crew would be aware of VMCG and there was training that if you did in fact lose one in that window, pull power on the opposite outboard engine slightly, put in full rudder and maybe a bit more than the standard 5 degrees of bank into the operating engines, and hope real hard that you can get fast enough quickly enough to keep it all together.  But there definitely was an element of additional risk in that operation.

This has an interesting effect that sometimes (when the aircraft is light) a derated take-off requires less runway. When Vmcg is close to Vr, the point where V1 is achieved if pushed further down the runway and thus the accelerate-stop distance is longer than take-off distance. Reducing engine power reduces Vmcg and that allows using a more balanced field length that will end up being a bit shorter.

Admittedly this answer is for civil operations, military trainers might be somewhat different. But Vef is actually entirely dependent on the V1 that you select. Vef is the point at which the engine is presumed to fail, for the manufacturer to do the calculations (the acceleration is immediately reduced at Vef). It must be at least 1 second earlier than V1, allowing time for the pilots to recognise the failure and react. Remember, V1 is the speed at which you must have commenced the actions of rejecting the takeoff, not just making the decision.
V1 isn't only the last point you can abort the takeoff though. It's also the point at which you know it is safe to continue the takeoff, and that's where Vmcg plays a major role.
Vmcg is the minimum control speed on the ground. With one engine producing full thrust and one engine windmilling, you have a significant yaw in the direction of the failed engine. This has to be overcome by rudder, but if you don't have enough speed/airflow over the rudder, it won't have enough authority to overcome the yaw. Vmcg is the lowest speed at which the rudder is powerful enough to combat the yaw.
So in summary: if the engine fails before Vmcg and you attempt to continue the take-off as you've already passed V1, you will run off the side of the runway. V1 must be equal to or above Vmcg. V1 is also at least one second above Vef by definition.


text:
Where is the MAP for the LDA RWY 25 at Eagle County Regional
The MAP for the LDA with GS is the decision altitude. The LDA without GS mins does not have a FAF to MAP distance, nor is timing given.

The missed approach point for the LDA without GS is CIPKU.  I agree the FAA charts are not as easy to read as the Jeppesen chart.

As indicated above on the Jeppesen plate, it’s much easier to see where the MAP would be at CIPKU.  Unlike RNAV approach plates, plates using terrestrial navaids do not mark the MAP specifically, but, by default,  use the final waypoint shown on the plate as the MAP.  Another indication would be where waypoint there the approach path changes from a solid line to a dashed line capped with an arrow, indicating the start of the missed approach segment of the procedure.


text:
How does a linear acuator in flight control work?

I see that the linear actuator moves the rudder but how? Thanks!

There are several types of linear actuators. The main three types are Pneumatic, Lead Screw Driven, and Hydraulic Linear actuators. In addition there are also solenoids and stuff but the three main types are used in heavy mechanical applications.
The one in the picture looks like a Hydraulic Linear actuator. The way hydraulics work is that the pressurized non-compressible liquid is forced into a cylinder using a pump. The pressurized liquid then moves a sliding wall inside of the cylinder. The sliding wall is also connected to the main shaft. When the liquid is pushed from one side, the sliding wall inside of the cylinder moves as the liquid pushes onto it, thus moving the main rod in and outside depending on the configuration.
Hydraulic linear actuators are used for mechanisms that reqiuire precision and high force / torque. İn this case, we want the rudder to move on a hinge that is placed on the root of the rudder. The linear actuator is placed on an lever that is offset compared to the hinge. Then, when the linear actuator moves, the linear movement converts to rotational movement and rotates the rudder surface.
Here is an image to help.

Welcome to aviation.stackexchange.com!


text:
What minimum equipment is needed to generate a METAR + MOS?
What specifically is the minimum equipment needed to generate a computerized METAR with:

Wind
Ceiling
Visibility
WX
Temp
DewPt
Altimeter
Density Alt
Clouds

and a MOS with:

Winds
Visibility
Clouds
Precipitation
Temp
DewPt

?

TAF I believe is put together by a real individual and may use MOS to aid in forecast. MOS on the other hand is completely automated

I don't understand the purpose of this question. Obviously the answer is: You need specialized equipment which can determine each of the relevant pieces of information (except density altitude, which can be computed). No?

The METAR report has accepted abbreviations and format and you simply must report them in that format, how you gather that information depends on what you are reporting, a lot of the regs can be found here:
You can report AWOS measurements which is information gathered from an Automated Weather Observation System and (here in the US) is governed by this Advisory Circular, your unit must adhere to those standards.
ASOS systems are automated as well and serve non aviation purposes beyond their aviation implications.
You can report ATIS which requires a human to actually confirm the measurements.
ARTCC facilities have meteorologists assigned to them to provide specialized briefings and tailor forecasts.
If you are just looking for a company that makes a compliant unit, heres one

The MOS reports are published by the NWS and are not "measured" so much as they are computed, it requires forecasts, prior observations and geoclimatic data to compute. The NWS defines it as

Model Output Statistics is an objective weather forecasting technique
which consists of determining a statistical relationship between a
predictand and variables forecast by a numerical model at some
projection time(s). It is, in effect, the determination of the
"weather related" statistics of a numerical model.


text:
Are there any published travel guides for GA Pilots?
Are there any published travel guides for GA Pilots specific to the US? Kind of like Michelin Guides, except for airplanes instead of cars and highlight scenic, historic or notable routes?

Baja Bush Pilots has guides for Mexico and Central America https://www.bushpilotsinternational.com/bpi_store/product_categories.php?category=2

This seems like a very broad question. Are you asking about a specific country or region? Even then, we typically don’t answer questions about information sources, because they can change frequently. If you’re asking about the US, you could start with AOPA’s travel page.

Wisconsin publishes one and even has a ForeFlight content pack. Other states may publish similar guides.


text:
Why don’t airplanes use turn signals?
Why don’t airplanes use turn signals like cars do? Would this improve safety for ground operations at uncontrolled airports? Could a similar concept be used to indicate in air maneuvers?
For example: a specific color could denote a right turn, a left turn, a climb or a descent.

At uncontrolled airports, there is rarely enough traffic for signals to be needed, and pilots should (though are not required to) communicate with each other on CTAF—an option that cars do not have.
In the air, if you're close enough to see a turn signal, you are way too close and need to immediately follow the collision avoidance procedure.
More generally, aircraft are a lot more like boats than cars, and boats don't have turn signals either.

Comments are not for extended discussion; this conversation has been moved to chat.

I suspect, like boats, planes do have turn signals. One is red, and the other is green. Both are always on. If you see the red one, you need to turn. If you see the green one, you don't need to turn....at least that is how boats work...

Turn signals for boats https://www.thamesvisitormoorings.co.uk/information/boating/sound-signals/

@Aron those navigation lights are only required to be on during the nighttime. They also don't tell you the pilot's intent, only the plane's orientation vis-a-vis your head.

I think the points raised in other answers are good, but they miss the essential difference. Cars choose from a discrete set of options, but planes do not.
When you indicate left when driving you are communicating to other traffic that either you are taking the next left turn, or that you're changing lanes (depending on context). In some situations the exact intention may be slightly ambiguous (is he indicating left for that driveway, or the next road?) but there are never more than a handful of possibilities which means that other drivers are able to transform the indication into the future behaviour by interpreting the information in context.
Contrast this with a plane with a hypothetical left indicator: where is it going? Is it going to turn by 2 degrees? 10 degrees? 50 degrees? More? Is it going to turn slow or fast? The indicator can't tell you, and the information in the sky can't tell you either. Add to that the complexities of communicating changes of direction in three dimensional space and you can see that the information communicated by an indicator - even if it was visible in time - wouldn't provide sufficient information to other planes to be useful.

On the ground might you suggest planes tend to have similar discrete options?

@JeopardyTempest I would think they have even fewer, no? That, together with lower usage, would probably render them pointless even without the many other systems that airports use to guide planes on the ground.

Aircraft have radios with which to communicate their intent. Cars do not. Pilots should be utilizing these radios even at uncontrolled airfields. A good mantra to have is that there are no uncontrolled airfields. Just pilot-controlled airfields. I will communicate my intent on the Common Traffic Advisory Frequency before entering the movement area of any pilot-controlled airfield. That includes before takeoff and after landing taxiing.
Aircraft have position lights, taxi lights, landing lights, anti-collision rotating beacons, anti-collision strobe lights, ground control, ground marshals, tower, TCAS, ADS-B, sterile cockpit rules (and recommendations for Part 91), runway incursion lighting, etc. with the limited traffic at Class G airports, a couple of more lights will not help.
On the ground, any pilot, aircraft or ground crew should remain well clear of an aircraft displaying all of its lights. And, by regulation, no aircraft should be in motion without displaying at least one of its anti-collision lighting systems. Even in the daytime (unless it was certified without a system). This is unlike a car. Cars can drive around in the daytime without headlights or taillights being on (not counting brake lights and turn signals).
In the air, red, white, and green lights are very distinguishable. Especially when close together at the wattage aircraft use. You would have to have high intensity lights to be able to distinguish between other colors like between red, orange and yellow; or between blue and green. When two aircraft are approaching one another at a closing rate between 100 knots and 1000 knots, pilots do not have the luxury of time to decipher light colors. Instead, pilots rely on the items I mentioned above as well as an explicitly spelled out right-of-way directive found in Title 14 of the Code of Federal Regulations Part 91.113.

§91.113 Right-of-way rules: Except water operations.
(a) Inapplicability. This section does not apply to the operation of an aircraft on water.
(b) General. When weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft. When a rule of this section gives another aircraft the right-of-way, the pilot shall give way to that aircraft and may not pass over, under, or ahead of it unless well clear.
(c) In distress. An aircraft in distress has the right-of-way over all other air traffic.
(d) Converging. When aircraft of the same category are converging at approximately the same altitude (except head-on, or nearly so), the aircraft to the other’s right has the right-of-way. If the aircraft are of different categories—
(1) A balloon has the right-of-way over any other category of aircraft;
(2) A glider has the right-of-way over an airship, powered parachute, weight-shift-control aircraft, airplane, or rotorcraft.
(3) An airship has the right-of-way over a powered parachute, weight-shift-control aircraft, airplane, or rotorcraft.
However, an aircraft towing or refueling other aircraft has the right-of-way over all other engine-driven aircraft.
(e) Approaching head-on. When aircraft are approaching each other head-on, or nearly so, each pilot of each aircraft shall alter course to the right.
(f) Overtaking. Each aircraft that is being overtaken has the right-of-way and each pilot of an overtaking aircraft shall alter course to the right to pass well clear.
(g) Landing. Aircraft, while on final approach to land or while landing, have the right-of-way over other aircraft in flight or operating on the surface, except that they shall not take advantage of this rule to force an aircraft off the runway surface which has already landed and is attempting to make way for an aircraft on final approach. When two or more aircraft are approaching an airport for the purpose of landing, the aircraft at the lower altitude has the right-of-way, but it shall not take advantage of this rule to cut in front of another which is on final approach to land or to overtake that aircraft.

Airplanes don't coordinate visually because they can't
The other answers are correct, but they all seem to miss an important point: airplanes barely see each other! Because (and in contrast to e.g. cars):

they can be anywhere in 3D, not just 2D on specific streets
they are incredibly fast (think of at least 2x the speed of a car on the highway)
they are comparably small (around the size of a car)

The difficult part is to spot another airplane. If two slow flying aircrafts (say Cessna 172) fly e.g. head-on, you may have 10-20 seconds to spot each other in reality. Trying to see detailed lights: impossible. But also not necessary: due to that, aviation does not rely on visual signs but uses:

radar for larger airplanes (or, in general, IFR when separation by ATC is provided)
pre-defined routes (e.g. circuits around an airfield)
conventions about on which height to fly into which direction
(sometimes) proximity warning systems
radio communication telling the position and intention where to go

The last point is especially important: compared to a car, when turning left, you have a continuum of 360 degrees (or 180 if we assume you take the shortest turn).
Furthermore, you have up and down.
Actually, it is even not uncommon for VFR aircrafts to request radar guidance instead of relying on visuals.
So what you care about is to know that an airplane, many miles away and not possible to see, is heading from x to y at height z. And this communication is done via radio.

I would add to this that VFR aircraft can receive radar advisories in some areas by requesting flight following.  More recently, it has become increasingly common for aircraft to receive TIS service via ADS-B.

There are pretty strict rules on how planes should travel on the ground. They are generally directed by ground control in the tower, and if they come upon another plane there are guidelines to who has right of way, and unlike car drivers, pilots generally know and follow the rules.

With our friend, Harrison Ford, being a notable exception.

@RockPaperLz-MaskitorCasket: The phraseology "continue holding" seems poorly chosen, since it's not hard to imagine that radio static could cause it to be misreceived as "continue ...oh...ing" and perceived as "continue going".  Unfortunately, there's no way of knowing what any particular transmission sounded like to the recipient unless the sound from the plane's receiver is recorded.

@supercat If there's any doubt at all, always ask for clarification.  So many mishaps could be prevented by following that simple rule.

@RockPaperLz-MaskitorCasket: True, clarification should be sought in case of doubt, but but radio static can sometimes result in things being obscured without being recognized as such.  Whether or not Ford is held to blame, I think the issue would likely have been avoided entirely if the controller's transmission had started with the word "wait" rather than "continue".  Phonetic alphabet letters are chosen to have distinct vowel sounds, and I think consistently using words with distinct vowels to distinguish concepts of "go", "wait", and "stop" would avoid confusionif consonants get mangled.

@supercat I agree! When speaking on a radio, word choice is just as important as accuracy.  Many years ago, I had to analyze hundreds of hours of ATC communication as part of research for my thesis.  Even in a quiet lab setting with no engine noise, I couldn't understand at least 20% of what ATC was trying to convey.  The same was true for what the pilots were trying to convey.

Not being in aviation, I would tend to think that the main reason that signals aren't utility for ground taxiing (which seems the most practical\potentially useful place) is that planes movement are generally setup to prevent the short reaction time we regularly have in cars.
"Reasonable" car spacing, and traffic lights, are such that there is often only around 3 seconds of reaction time.  This is usually sufficient if the change can be properly identified, because vehicle size and dynamics allow for quick changes (some exceptions apply).  Whereas aircraft are primarily designed for flight, and so I would think may not be as setup to be as adept at sharp ground maneuvers compared to even the more challenging vehicles like semi-trucks.
In addition, I would figure there are expectations of complex distractions (flight checklists) for much of the ground travel time on aircraft, and so I'd expect that ample spacing is fundamental.
As such, taxiing doesn't tend to do things like multi-lane traffic or high traffic intersections.  And with everything spaced out more, the sudden dangers of traffic slowing to turn or conflicts when moving into new lanes doesn't exist, and turn signals have fairly limited use.  Plus there are comparatively few travel ways, with fairly regular movement for most vehicles, such that people know the spots to expect turns and stops.
If anything, maybe brake lights could be of more use, as I'd think planes are more likely to stop in random places than turn in random places (and brake lights would take care of highlighting unexpected stops made to perform a turn).

I tried to find any rules for taxiing distances, but could not easily do so.  If anyone knows where to find those, that would be an interesting addition to test\verify the thinking.

This also got me to thinking how useful variable brake lights might be in driving!  Because properly identified being key, a sudden slam of the brakes on an interstate can be a very tough thing to recognize (compared to tapping the brakes).

Aircraft accidents are not caused by "that plane made an unexpected turn", but by "that plane came out of nowhere".
Also, cars operate on a flat surface. There are 3 choices: Left, Right, Straight.
Aircraft maneuver in 3D. How would turn signals express a climbing turn? A loop?

Although all of these answers are very good (and correct), they are missing an important fact: planes try to go on the most direct routes (unless mountains, or other landmarks that affect flight, are in the way). This means that most planes will be traveling in a straight path, so turns aren't applicable. That too planes are given routes that do not travel close to the same point at the same time (to prevent a collision). This means that contact (besides at airports) is rare.

Planes (or actually pilots) are in fact not as free to choose their paths as one might think. Only low alt VFR flights enjoy somewhat extended freedom, higher up, not so much. Even low down there are airspace limitation and mandatory entry/exit points, so straight flight between A and B is a rarish treat.

Before travel, pilots must file a flight plan. Unlike cars, drivers can leave anytime, and choose any route without notifying anyone; some drivers even don't follow road rules and ignore traffic lights while some even drive on pavements & traffic islands or turn/change lanes without indicating anyway

@Zimba Flight plans are not required for all flights in all countries.


text:
Why might flight schools prohibit you from testing pitot heat during pre-flight?
Why might flight schools prohibit you from testing pitot heat during pre-flight? I know of a school in Texas that has this policy but don’t understand why.
Here is a snippet of the C172 AFM which lists testing pitot heat for normal pre-flight procedures. The aircraft is not ice legal anyways but still seems like a good idea if you (although unlikely in the region) inadvertently enter icing conditions.

Why were the comments deleted??

++1 to that. I found the comments supplementing the question effectively!

Comments seeking clarification, where clarification had been given (and updated into question) were no longer necessary. Comments which are pseudo answers were removed as per policy see also this meta question. Conversation is better suited to chat

I was taught to check it (on a C152/172) before every flight but I've also heard people say that you don't need to. Some reasons I've heard people give for not checking it are:

Risk of draining the battery to the point where you can't start the
engine
Risk of burning your hand on the pitot
Risk of forgetting to remove the pitot cover and melting it onto the tube
The POH doesn't include it in the preflight checks so it can't be important

Note that you can avoid most of those issues by using a checklist.
You can check what the POH says, e.g. the C172S POH includes it in the preflight but the C172M one doesn't. But even if the POH doesn't mention it, you should always check it before operating in IMC.
It would be a great question to ask the school or an instructor there, especially if the aircraft's POH does say you should check it.

I'd think the last paragraph is the key item. If the school is contradicting the POH, it's up to them to explain why.

@757toga, I've seen a video of crossing I think Canada to Greenland in a C210 where their pitot clogged up in VMC with fairly good visibility (I think they were above layer of clouds, but it was clear at their level). Turning on the pitot heat fixed it after a while. So clearly the pitot can pick up some ice even in what isn't otherwise considered icing conditions.

This is a fantastic, complete answer.  The primary reason is to avoid accidentally running the battery down when a student forgets to turn the master and pitot heat switch off, because this grounds the airplane for hours, cancelling numerous scheduled flights.
For a flight school in Texas, icing is not likely, particularly if they only do VFR Private training and no IMC.
In my opinion, the checklist should read: Pitot Heat: CHECK if flying IMC (or if OAT at planned cruise altitude is below 10C/41F). It is SO easy for a CFI to train a student to never leave the master or pitot on though...

@757toga, the scenario is that the student goes out to preflight, forgets to turn off the master and pitot heat, and comes back in to meet the instructor and do the pre-flight briefing, complete with weather briefing and filing flight plan.
Leaving the master and avionics on on a G1000 can do it too, if it is for a long time (I don't remember how long though- none of my students ever did such a absent minded thing!)

@757toga, Sometimes the instructor (me) might be slightly behind schedule from the last lesson, filling out part 141 training records for the student who just walked out the door when the next student (who has done a dozen of preflights alone) shows up 10 minutes early... so while I'm finishing paperwork or filling out the previous student's logbook they can kill time by preflighting and then come back in to meet with me for pre-flight brief and wx check.  When we get to the airplane we make sure a vehicle didn't run into it with a quick visual walk-around.


text:
What happens if you take off with a direct tailwind?
What happens if you take off with a direct tailwind?

It takes longer.

Do you mean taking off in the same direction that the wind is blowing? This is called taking off with a tailwind.

You'll break it sooner as you climb.

Related

Perhaps you can expand your question? Simply repeating the title doesn't give us a good idea of what information you're looking for, and what you know already.

is it common in airfields to change the direction of takeoff on the runway to get favorable headwind rather than tailwind?

@FlorianCastellane Yes, it is. That really belongs more as a question than as a comment, though.

Given how few bounding criteria you have in your question, the general result is

For fixed wing aircraft: your ground speed will be significantly
higher than if you'd taken off heading into the same wind, and thus
you'll tend to use up more runway before lifting off.
Example: with a take off speed of 100 kts, going into or downwind is the difference between 90 knots or 110 knots ground speed before reaching take off speed when the wind down the runway is 10 knots.  This difference becomes more pronounced as wind speed increases; it's a differential of 2 x wind speed.
With a long enough runway it won't matter in terms of "taking off before running out of runway."  On a short field it may matter a great deal.
For Rotary Wing aircraft: you may need a bit more power to hover when
lifting off with a tail wind.  The FAA has this guidance:

Headwinds are the most desirable as they contribute to the greatest
  increase in performance. {snip} When taking off into a headwind,
  effective trans lational lift is achieved earlier, resulting in more
  lift and a steeper climb angle. When taking off with a tailwind, more
  distance is required to accelerate through translational lift.

For a variety of aircraft types, if the tail wind is high enough your manual will recommend against/prohibit down wind takeoffs, but that varies enough between models and types that a general answer can't encompass all of the variations.

Add something about the "gustiness" too?  If the wind is varying between 5 and 20, then your effective airspeed at take off might suddenly drop 15 knots leading to a loss of lift and a sudden return to not-flying.

@Criggie You'll have this effect too when starting against the wind. but off cause it will make the "out of runway" problem worse.

@Criggie -- "a sudden return to not-flying", nice.  As in, "Oh my god, the engines are on fire!  We are going to suddenly return to not-flying!"

@Criggie the question as asked is about a direct tail wind.  I don't disagree with your point on gustiness, but won't that have a similar effect into the wind, albeit you'll have lower ground speed (and that runway's end is approaching faster!)

"For Rotary Wing aircraft: you'll need more power to hover" -- this is not true. The only factors for hover performance in a heli are density altitude, weight, and surface (hard or soft).  Translational lift can occur at any angle to the fuselage, because the (rotary) wing is 360-degrees.

@rbp Many rotary wing aircraft have a slight forward tilt/bias to the disc.  Lifting off into the wind takes advantage of that as you are getting a free (x) knots progress into the translational lift, however, I am sure there are some twin rotor types (CH-47) where this is all washed out, or insignificant, and others where the bias is less.  T/R helicopters do have some tail wind/rearward flight limitations in their operating manuals, but how much varies.  Is the power differential significant? All other things (the standard factors you mention) being equal, maybe not. Slight edit.

@rbp Put another way, I often found that flying backwards took a bit more power than forward, which is what taking off with a tail wind amounts to (flying backwards) but that might be very "model dependent" ...

There are always type differences. I gave the aerodynamic answer.

@rbp And I gave the practical answer: theory and practice have a neat relationship. :-)

So I will focus on fixed wing aircraft, as that's all I really know about.
Lift is a factor of your "Indicated Airspeed". So the faster the wind is going over the wing, the more lift the wing can generate. You always need a certain Indicated airspeed to take off. The plane simply won't "go up" until you reach that speed. Depending on the aircraft, the needed speed of the air over the wings changes.
For example in a Cessna Grand Caravan you need about 80 knots of Indicated airspeed to really take off. There are some "rules" in its handbook about short take-offs, but in general you want to be above 80 knots IAS before you start "going up".
Now if the wind is constant, and blowing from the front of the craft to the back at 5 knots, then you already have an IAS of 5 knots. Sitting still your IAS is 5 knots, because the air is passing over your wing at 5 knots.
If that wind is passing from the  back (tail) or the aircraft to the front, then you have a IAS of -5 knots when sitting still.
Now we get into ground speed. Mostly when you're flying (in the air) you don't really care about ground speed, other then efficiency and as a measurement of where you are. If you care about it at all it's way back at the end of the list. You care more about IAS (to keep you up) and True Air speed (the speed of which you're actually moving through the air). But when you're taking off or landing you care quite a bit about ground speed.
So generally 1 knot of IAS would be equal to 1 knot of ground speed. So to get our sample plane off the ground, on a day with no wind, you have to be moving at 80 knots on the ground. That's roughly 92 miles an hour.
With a headwind (from front of the plane to back) of 5 knots you have to be moving at 75 knots ground speed or 86 mph.
With a tailwind (back of plane to front) of 5 knots you have to be moving at 85 knots of ground speed or 97 miles per hour.
Depend on your how your plane is designed, those few knots of ground speed can mean the difference between a good take off, and running out of runway. Or because the wheels are actually on the ground, exceeding the safety of the structure of the landing gear.
Lets take a runway of 2000 feet. There are smaller runways, though to be fair this is a pretty small one. The example plane needs 1,160 feet to take off in a situation with no wind and empty. So we could take off from this airport. There's a "rule of thumb" out there that says "operation with tailwinds up to 10 knots, increase distances by 10% for each two knots [of wind]." So at 5 knots of tailwind I go from needing 1,160 feet to about 1,500 (error on the side of caution). I can still take off, but what about weight? Different weights need different lengths to get up to speed. Another rule of thumb "10% change in weight will cause at least a 20% change in takeoff and landing distances." So for are sample aircraft lets say I have a total weight of 6,000 lbs. The Empty weight is 4,550. That's a weight change of around 31%. So now I need to add on 60% distance to my ground roll.  So I need 1,900 feet to take off (again pad for caution). I'm still good. But let's add in the wind. Now I need 2,375 feet to take off and the runway just isn't that long. So I'm stuck on the ground.
So our example in summary:

With no wind. I can take off
With a headwind, I can take off
But with 5 knots of Tailwind I can not take off.

SUPER IMPORTANT NOTES

Rules of thumb are great, but they're not the POH. Every airplane should come with a POH (and I mean every physical plane should have a POH in it). In that POH are real limits, and real rules/guidelines. Most will contain a table or chart that spells out weight, ground roll and wind speeds in one way or another. Some craft will have safety limits, that should not be exceeded.
The rules of thumb are great for conversations in general but should not be applied to an aircraft in real life. If you're flying a plane you should know the plane's specs and limits. Not just "guess" at them.
The numbers I used in the example are accurate enough for an example, but come from Google.
Runway length is also effected by what it's made of. Grass fields take off "longer" then asphalt.
Runways can be as short as 800 feet, but most larger airports have
runways in the 10,000 feet range. The longest public runway is about
18,000 feet. There are runways that are longer.
While the runways may be bigger the jets that use them need to go faster and take longer to get there, so the problem exists for them, too. More so, in some ways.
A lot more then just IAS goes into a take off there is air density, for one. The slope of the runway, the temperature of the air. This example is really simplified to look at the one aspect.

"In that POH are real limits, and real rules/guidelines." Most of the "limits" regarding wind in POH's are demonstrated limits, not absolute limits. So I wouldn't call them "real limits" or "rules". Also, there were a lot of aircraft manufactured that never had POH's. Only other thing I would say is that most larger airports do not have runways 18,000 feet long, about 12,000/13,000 is the largest you'll find on public airfields.

While I agree that the limits are not as limiting as they sound, I thought all aircraft had to have either a POH or an AFM. Could totally be wrong. Also on runway length, I meant that as a max. I will clarify.

Two risk factors which have not yet been mentioned:
The higher groundspeed required before airspeed is sufficient for take-off will put higher strain on the landing gear and wheels. Imagine a bump in the runway; hitting it at 80 or 100 mph will make a difference which in the worst case may cause e.g. a wheel puncture.
Also, should you need to abort the take-off, the braking distance before the airplane comes to a stop will be much longer from 90 mph than from 70 mph. The stopping distance will be 1.65x longer, although the speed difference in this case is only 1.28x.
Came to think of a third risk factor too: Wind gradient.
Often the wind blows stronger the higher you get above the runway. This can be significant at small airfields. In a normal take-off with a headwind this helps the airplane climb better as it ascends. But in a tailwind take-off the tailwind increases as the airplane ascends, meaning that the climbing rate is reduced (nose must be held down to achieve sufficient airspeed for climbing). If the airplane has sufficient power this may not be noticeable, but a marginally powered plane may have difficulties if there are obstacles close to the field.

Very important points.

You will need more runway. Once airborne, there will be no difference, apart from an unfavorable wind gradient.
Besides, it is not advisable, because, in non-controlled airfields, the pilots consider the runway with a headwind as the active runway.

Third sentence ought to be in bold. This is vary important in GA.  +1

The airplane will still fly; it just takes considerably more runway to depart.  Most Pilot's Operating Handbooks (POHs) will use a phraseology in their takeoff roll performance charts such as "increase ground roll 10% for every 2 kts of tailwind" or similar.  Doesn't look too bad but consider now that if you depart in a direct 10 kt tailwind, your ground roll and distance to clear a 50 ft obstacle is now 50% greater than a takeoff in still air.  This become a serious factor on short airstrips and high field elevations and density altitudes.  A Cessna 172 may require 1300 feet of runway to do this at sea level at STP but might be upwards of 5000 feet of runway needed for a 6000 ft field elevation at 30° C.

Jump-pilots and Ag-pilots regularly take off downwind and/or with strong cross-winds providing of course the runway is long enough.  A dedicated airport is preferred.  If you want to get tremendous experience as a pilot, fly 500 hours taking skydivers up to 11,000 feet.  You are dropping falling bombs that become floating bombs that pass through winds aloft from different directions at different altitudes then land on the drop-zone target.  You'll know you're a respected pilot when the experienced jumpers fall asleep during the climb.  You will learn how to say NO! when your boss pushes you to the limit with weight, weather, and flying with minimum fuel.  Most jump-planes look fairly junky and it's fun to tell first time jumpers when they see the airplane, "if you think the airplane looks bad you should see the parachute!"

This doesn't really answer the question. The fact that some operations are willing to accept tailwind conditions with a long enough runway and/or a dedicated airport does not describe what happens if you take off with a direct tailwind. The remainder of the commentary is interesting but irrelevant to the question. See more on what to put into an answer here. Welcome to Aviation.SE!

"Once you lift off, there's nothing to worry about".... The increased ground speed may cause you to believe (optical illusion) you have a faster airspeed and the desire to increase your pitch attitude.(Which may be already high due to the lengthened take off roll and the need to climb). Your climb rate will suffer also. (vertical gain vs. horizontal travel). This goes against the bottom line...." Never regret NOT having the air above or the Runway behind you." My personal minimums will not accept a downwind take off OR landing ( also a major optical illusion) greater than 5 Knots.

The other answers and comments are ignoring an effect that usually does not show up in practice, but that it exists and I have witnessed first hand: as long as the air flow on the frame is reversed, so is the effect of the commands.
For take off, the effect diminishes as the aircraft gains speed, so it will probably only affect gliders and other light aircraft that rely heavily on the commands since the start of the run. On landing, the effect increases as the ground speed diminishes, and I have witnessed a serious crash (straight against a fence that run at the side of the runway) because of it.

You'll have reverse airflow over the controls only as long as your groundspeed on the takeoff roll is less than the wind speed

That's exactly what my answer says. And, as I mentioned, the effect increases when groundspeed decreases, so it can be deadly on landing.

Good point, but the question is about take off.

It could still be deadly on take off, on a extreme situation (say, 80km/h tail wind on a J3). Usually, not pilot is crazy enough to try to take-off with a heavy tailwind, but it is certainly possible.

the controls only reverse with a tailwind when the wheel is on the ground.

Yes, absolutely: as I said, "as long as theh air flow on the frame is reversed". I saw a friend fight for his life for two months at the hospital because of this.

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Is a one foot landing possible?
This video shows an aircraft touching down like a helicopter on some gravel, is this possible or is the video a fake? Are there any other videos out there?

Facebook video
Similar one on YouTube

Is it possible to find this on YouTube?  Many of us do not have Facebook accounts.

@Simon You don't need a Facebook account to view it.

@J.Hougaard Ah, I  see.  Sorry, not familiar with the workings of the book of the face.  I didn't realise that you can bypass the login.

@Simon: Facebook is happy to receive visits from non members.

This sounds so very much like a duplicate, but I can't find another one with my limited search knowledge...

Imagine you have a 60 knot headwind. You have to fly an indicated airspeed of 60 knots and you can hover over the ground.
If you want you can try it out in flight sim, it makes lots of fun.
That's called a STOL.

It's a STOL (short takeoff and landing) plane, landing in strong headwind. It's perfectly possible.
You can find more examples on YouTube.

With a STOL aircraft like a Carbon Cub or Aviat Husky and brisk headwinds, it sure is.  Alaskan bush pilots have held landing competitions with these to see who can stick a landing - literally set down and hold the wheels in that spot.  The videos you reference are real.
UPDATE:  this guy officially set the world record for a fixed wing STOL aircraft landing in still air with a 10ft, 5in ground roll!
https://www.facebook.com/valdezflyin/videos/10155067657750071/

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Can you push the throttle forward while using reverse thrusters?
Can you push the throttle forward while using reverse thrusters (for turbofans)? Does this have any effect, such as strengthen the "reverse" air blanket? Is it ever used?

What type of aircraft are you asking about?

I had some popular commercial turbofans in mind. E.g.: 737, 747, 777, 787, 320, 330, 350, 380. I've edited the question to specify.

On typical Boeing throttles, this example being a 737NG but similar on all Boeings, the reverse thrust levers must be lifted to engage reverse.  In order to do this, the thrust levers must be in the idle gate and cannot be advanced until the reverse thrust levers as stowed.  The reverse levers engage locks in the thrust levers. In this video, at 2:50, you can see the thrust levers being retarded to idle, then the reverse thrust levers being pulled up.  At 3:22 they are stowed.
In this video from an A321, you can see that the Airbus system is very similar.

Is it possible to reduce the reverse thrust by pulling the reverse levels up halfway? Or must they be fully engaged to work at all?

The Airbus system does not strike me as particularly similar.

Yes.  In reverse thrust, at idle, there is no effective thrust.  Advancing the throttle provides beta thrust.

Is it normally advanced all the way?

On which aircraft?  I've never heard of beta thrust.  Are you perhaps thinking of beta on turboprop aircraft? On Boeings and Airbus, advancing the thrust levers will stow the reversers.

Cessna 208B for a turboprop example.

I assume that the OP is asking about turbofans and turbojets.  We need to clarify.

A friend who flew B727 told me years ago about using their engines for push-back, and that certain airports had been upgraded to withstand the forces on the terminal building windows.  I suppose that would be an example of a non-turboprop.

@TayE reverse thrust should not exceed the torque limits. Also it is not approved for more than 60 seconds.  While it is very helpful managing taxi speed without brakes, and shortening landing lengths, some also use it for push back.  Personally, I have only done that with ground observers, although many pilots will clear the area behind them themselves prior to engine start.

@Terry, in the 727 if the clamshells are deployed, is there effective thrust?

Okay, I didn't see your qualification of when the reversers are deployed as to whether there is effective thrust in your answer. I don't know whether all 4 engines on the 747 with reversers deployed will start the airplane rolling, so I have deleted my comment. Sorry about that. I used to occasionally back up the 727. It always took a burst of power to break away, and then we reduced power considerably but I can't remember whether we went all the way to idle and kept moving.

Today I talked with a friend who frequently did push/power backs in the 727. The procedure involved a trained ground crew and a signed off capt. The ground observer would signal a small forward thrust, followed by reverse thrust. Slow movement. Then forward thrust to stop the backward movement. This saved tugs and tug operators, but required ramp FOD inspections, etc.


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Do you have to update weight and balance charts after installing new avionics?
The POH always has weight and balance charts. Let's say you install some new avionics, hence changing the weight of the aircraft. Do you need to update the POH binder with new weight & balance charts? What about take-off/landing distance information?

Are you interested in a specific country or regulator? The general answer is yes, but if you want pointers to regulations then you should mention which country you want to know about.

For the US under the FAA, Yes you do!
From the FAA WB handbook

Changes of fixed equipment may have a major effect upon the weight of
  the aircraft. Many aircraft are overloaded by the installation of
  extra radios or instruments. Fortunately, the replacement of older,
  heavy electronic equipment with newer, lighter types results in a
  weight reduction. This weight change, however helpful, can cause the
  CG to shift, which must be computed and annotated in the weight and
  balance record.

For larger repairs.

Repairs and alterations are the major sources of weight changes. It is
  the responsibility of the FAA-certificate mechanic or repairman making
  any repair or alteration to know the weight and location of a change,
  to compute the CG, record the new empty weight and EWCG in the
  aircraft weight and balance record, and update the equipment lists.

Generally this is done by the shop that installs them. If you as the owner/operator installs them (which you are permitted to do to some extent) you may need to have a new WB drafted up.
This is also checked at anual every year,

The FAA-certificated mechanic or repairman conducting an annual or
  condition inspection must ensure the weight and balance data in the
  aircraft records is current and accurate. It is the responsibility of
  the PIC to use the most current weight and balance data when operating
  the aircraft.

There is no requirement for this information to be carried in the POH. The weight and balance records are generally part of the aircraft logbook.

There is however a requirement for it to be in the AFM as per § 23.1583

Regarding the following quote: "which you are permitted to do to some extent", non-mechanic operators are generally prohibited from performing repairs or alterations which would impact weight and balance.

But they are more than legally aloud to install tray based avionics (which falls into the question here) hence the "to some extent".

There is however a requirement for it to be in the AFM as per § 23.1583 No, that is incorrect. §23.1583 only specifies maximum weights and CG limits. This is generic information, just as would be included in a POH.

@JonathanWalters I don’t think it’s accurate to say that the W&B is part of the  aircraft’s logbooks. The factory provides an original W&B as part of the Aircraft Flight Manual. As things are added and removed a new W&B is made that shows the changes. The new W&B is kept in the aircraft with the AFM and POH. It is true to say that older versions of the W&B are usually kept with the logbooks, mostly to be sure a mistake wasn’t made along the way.

@JScarry you are correct that weight and balance information is generally provided with the AFM (but not by FAA requirement!). And you are correct that this information is generally updated as a way of updating weight and balance info. However, note that an AFM is different than a POH. As a mechanic, I have always kept separate, detailed weight and balance information in logbooks.

@JonathanWalters I am only familiar with the logbooks of the three airplanes I have owned, and when a new W&B is made, a notation is made that says something like, "See WO #xxx and 337 for details", and/or "Weight and Balance amendment made to reflect the change". A line is made through the old W&B and a notation made on it, "Superseded by W&B dated xx-xx-20xx".

@JScarry Yes, that is a good way to do it.

Yes, the empty weight and center of gravity data does need to be updated.
Anytime weight or center of gravity is changed, the mechanic must update the aircraft weight and balance. This information must be available to the pilot prior to flight, and is often included in the POH as an additional sheet or otherwise copied into the flight manual. In this way, the answer to your larger question is, yes.
However, if you are referring to the generic charts for the purpose of calculating weight and balance, the answer is no, these generic charts do not require updating. Conversely, an approved Airplane Flight Manual (AFM), will generally include weight and balance information that is specific to that aircraft. This information should be updated, or a note should be made invalidating the outdated data and referring the flight crew to the current data.
Typically when a change such as avionics installation takes place, the mechanic will compute a weight and balance change based on the item weight and installation position. However, the aircraft can be re-weighed to satisfy the same requirement.
The FAA states that mechanics should update the weight and balance record whenever an alteration such as an equipment change takes place. See the following paragraphs from page 1-3 of FAA-H-8083-1B, the "Weight and Balance Handbook".

Changes of fixed equipment may have a major effect upon
  the weight of the aircraft. Many aircraft are overloaded by
  the installation of extra radios or instruments. Fortunately,
  the replacement of older, heavy electronic equipment with
  newer, lighter types results in a weight reduction. This
  weight change, however helpful, can cause the CG to shift,
  which must be computed and annotated in the weight and
  balance record.
Repairs and alterations are the major sources of weight
  changes. It is the responsibility of the FAA-certificate
  mechanic or repairman making any repair or alteration to
  know the weight and location of a change, to compute the
  CG, record the new empty weight and EWCG in the aircraft
  weight and balance record, and update the equipment lists.

Note that the aircraft weight and balance record is generally a part of the aircraft maintenance logbooks, which are typically not carried on board the aircraft. The change in weight and balance is typically noted in the POH by inserting a photocopy or otherwise transferring the applicable information. In regards to these choices of where to store the required maintenance information, including the current weight and balance data, the operator is often free to choose according to convenience. There is no general requirement in 14 CFR to carry current empty weight and center of gravity data on board the aircraft for flights operating under §91.
Flights operating under 14 CFR, Subchapter G will, or may, have different operating requirements. For example, an air carrier authorized to operate under §135 is generally required to carry, on board the aircraft on flights operated under §135, a completed load manifest documenting weight and balance computations. However, for flights operated under §91, such documentation is not generally required.
Note: This answer addresses operations under FAA jurisdiction.

I did not downvote, but anytime you change the equipment in an aircraft, a new weight and balance must be computed. The POH must be updated to include the new weight of the aircraft, usually this is done with a supplement which has to be kept in the aircraft. I just went through this in my aircraft when we installed the Garmin GTX345. The weight changed by a whole pound, and the paperwork probably weighed more than the changes.

@RonBeyer So did you go through it all again with the changed weight of the written material? (tongue in cheek)

To whomever downvoted, I would be interested in understanding what I have gotten wrong. Thank you.

@JonathanWalters The POH is not always generic, mine is serialized and tied to my airframe. It includes specific equipment, weight, and balance information. That information is invalidated when new equipment is installed.

@MichaelKjörling You mean the large envelope of paper the avionics shop gave us and we threw in the back? I know it has paper in it :) They also were nice enough to give us a USB drive with all the new paperwork on it, I did read the manuals, but not the supplements.

@RonBeyer Something like that, yes. :-)

To be clear, the W&B is a document required for flight. It could be merged with the POH, but is regulatorily distinct.

@Mongo Is it? For §91, I mean? No, there is a common misconception, widely held, that current weight and balance documentation is required to be on board an aircraft for every flight (see the marginally helpful ARROW acronym). This is not true in any general sense. In some cases the aircraft TCDS will require it, and operations under §135, among others, requires it. But for a C172M, for example, there is no requirement to have current weight and balance documentation on board the aircraft.

I'm a little confused why you first say no then yes.

@TomMcW The original question is unclear, insofar as the OP refers to charts. Most weight and balance charts are generic. In this way, no, these generic charts do not need to be changed. However, the larger question is whether or not the weight and balance data needs to be updated. The answer to this is, yes. But there is no blanket requirement for this data to be included in a specific place, it need only be appropriately recorded and made available to the flight crew prior to flight.

Yes, any change in equipment attached to the aircraft requires a new weight and balance update.  The weight and balance data are required for flight, but a photocopy is acceptable.  In most operations I have been involved with, there is a binder or folder of required papers, and W&B is stored there, along with radio licenses, etc.  POH formats vary, and some are not in binders. As a matter of practicality, the current W&B data must be readily available to the pilot and crew.

Having current weight and balance documentation on board the aircraft for flight is not, in fact, a general requirement for operation under §91. Some aircraft TCDS may require it, but 14 CFR does not. That the weight and balance documentation is included, as a matter of practicality, in the documentation available on board the aircraft does not render it part of the required documentation for all aircraft operating under §91. Operation under other parts—§135, for example—is a slightly different matter.

Whether a flight is within the operating limitations of the aircraft is predicated on having W&B data. Without the data, the determination cannot be made.  Whether that data is in a W&B worksheet, the POH specific and amended for that aircraft, or scribbled on the back of someone's hand does not matter, but it must be available. Practically, a photocopy of the W&B is the easiest and a common way to have it readily available.

The calculation needs to be made, or the determination must otherwise be made, but no written documentation of that is required, nor is any such documentation required to be on board the aircraft. This is not the case for §135, but that is a different matter. In this case of an alteration leading to a change in the empty weight and/or balance, the current data must be recorded and available to the pilot, but need not be in the POH, nor on board the aircraft.


text:
Is the Cirrus SR22T a turbo-prop? Or does in just have a turbocharger?
Is the Cirrus SR22T a turbo-prop? Or does in just have a turbocharger like in a car?

It is a turbocharged piston.

It is a turbo charged piston aircraft (much like turbo charged car, the engine is somewhat similar to that found in the older air cooled Porsche 911's (think 930 turbo)).
Turboprop is generally short for Turbine-Propeller which is a propeller aircraft powered by a turbine engine.
Turbo charged piston aircraft are piston driven engines with a turbo charger, many often may carry the T or TC designation after the model number. Such as the Piper Saratoga TC or SR22T
In this case we can reference the SR22T's Specs from the website

Airframe & Powerplant
Continental TSIO-550-K 315 HP Turbocharged Engine


text:
Why is this plane flying a circular track?
Came across this on flighradar24 recently. It shows a jet making a very strange pattern. I would normally expect it to be some sort of aerial survey but seems unlikely in such a large aircraft at such a high altitude (I would expect to see a GA plane do this at lower altitudes).
Snapshot:

Closeup of snapshot:

Flight details (still might be able to find flight if you hurry and check out the latitude and longitude):

apart from telling you that the aircraft is flying in circles and the cutting lines are a glitch of flightradar24, what do you expect us to say? (considering the possibility that the mission was military and as such anyone with a knowledge of it would not be able to answer you)

The aircraft information may be incorrect. I'm interested in how FlightRadar figured out that it is a Bombardier Global 6000 without having the Mode-S code, serial number, or registration number.

A recent article in Aviation Week showed a modified Bombardier Global 6000 with a "canoe" type fairing underneath the fuselage which typically houses a variety of radar or electronic intelligence (ELINT) equipment (link (free registration req'd) with pic) (alternate). The UK's RAF flies the Sentinel aircraft which is based on a prior Bombardier model, the Global 5000. So it's certainly possible that the track is a valid orbit path for surveillance in that area.
The USAF E11A is based on a Global 6000. It carries the BACN battlefield communication relay system which allows integrated, real-time communication across several, sometimes incompatible platforms. It is designed to operate at high altitudes to allow coms over mountainous terrain.
Since the Jalalabad airport is currently controlled by US armed forces from the adjacent Forward Operating Base Fenty, it would make sense that a communications aircraft would loiter over the area.
If it is a military flight, it looks from the flight path that it may have originated from Kandahar, where the USAF has a base.

(Source)

This may be a better explanation than mine given the altitude of the aircraft involved -- most flight checks are conducted at rather low altitudes (usually around the MSA for airways and service volume checks)

I edited in some additional information. Hope you don't mind. You can roll back if you want

You know some engineer was hungry when they named it BACN.

@TomMcW Thanks for the additional info!